Are there bonds which share single electron?

During chemical bonding, I asked our teacher why there are only 2 electrons shared in a bond. He said that because it's that one orbital can accommodate only two electrons. Two electrons make it stable. He said that there are bonds which share a single electron which has some term I don't remember and is out of our understanding for now. So, I am curious whether there are such bonds, what are they called, some examples, and are they unstable due to the reason aforementioned?

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    $\begingroup$ Not exactly a single electron in one bond, but there's other examples like 4c-3e in PCl5, or 3center-2electron bond in diborane. There are unpaired non-bonding electrons like in nitrogen dioxide. But, I am unaware of a single electron in one bond. $\endgroup$ Mar 24, 2018 at 17:26
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    $\begingroup$ en.wikipedia.org/wiki/Dihydrogen_cation $\endgroup$
    – user7951
    Mar 24, 2018 at 18:20

1 Answer 1


There exists an interesting molecule dicarbon with bond order two and two pi bonds instead of the usual one sigma and one pi. This is the case when 2s-2p mixing is allowed in molecular orbital theory. However when the aforementioned condition is not allowed, dicarbon exists as a molecule with one sigma and two pi bonds of, interestingly, one electron each. So in a way, one electron bonds do exist.


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